Fine structure cytochemical localizations of five types of retinal synapse will be carried out. Synapses to be studied are those mediated by the neurotransmitters: acetylcholine, glycine, GABA, taurine and dopamine. Synapses mediated by acetylcholine to nicotinic receptors will be localized by use of horseradish peroxidase conjugated to alpha-bungarotoxin. Reaction product will localize along the post-synaptic membrane and taurine and dopamine will be localized by use of electron microscopic autoradiography to demonstrate sites of accumulation of tritium labeled compounds. Label accumulation will be observed within specific neuronal terminals and the originating cell bodies and processes. Pre- and post-synaptic elements at each specific chemical synapse will be identified. The distribution of these synapses within the retina will be analyzed and the originating and receptive neurons for each chemical transmitter described. Each chemical-specific synpase localization will be carried out in cat retina to provide data for development of a circuitry diagram of chemical transmission in that mammalian species. This study will facilitate correlations between morphologically defined subclasses of retinal neurons and observed electrophysiological responses to particular transmitter substances. In addition, principles of chemical organization described in the retina may find widespread application throughout the central nervous system.